1. Field of the Invention
The present invention relates to a high damping capacity alloy having high damping capacity more than 2.times.10.sup.-3 over wide temperature range and more particularly to a high vibration damping capacity alloy having good cold workability and high corrosion resistance.
2. Description of the Prior Art
Recently, elements or members made of alloys having damping capacities have been widely used in precision instruments susceptible to vibrations, and machines such as aircraft, ships, vehicles and the like causing vibrations and noises for the purpose of mitigating the public nuisance resulting from the vibrations and noises.
In the prior art, alloys of Mn-Cu, Ni-Ti, Zn-Al, etc. having values of Q.sup.-1 more than 0.005 have been commonly used. The value of Q.sup.-1 indicates the inherent damping capacity of the alloy against vibration. When a body is vibrating in a damped oscillations, there is a following relation between first and n-th amplitudes A.sub.o and An of the vibration. EQU An=A.sub.o exp(n.delta.),
where .delta. is logarithmic decrement and indicated as .delta.=.pi.Q.sup.-1. On the other hand, if the vibrational energy E decreases by .DELTA.E during one cycle, a relation between the amplitudes An-1 and An is expressed as EQU .DELTA.E/E={(An-1).sup.2 -An.sup.2 }/An.sup.2 =2.pi.Q.sup.-1.
In other words, Q.sup.-1 is a function of the energy decreased during one cycle. The larger value of Q.sup.-1 decreases much more energy of the vibration so that the amplitude becomes smaller in a shorter period of time to exhibit a higher damping effect.
The alloys of Mn-Cu and Ni-Ti among the damping alloys of the prior art are superior in the damping capacity characteristics at room temperature to that of other alloy. However, as the temperature becomes higher, the damping capacity decreases rapidly and becomes substantially zero at the temperature near 100.degree. C. such that the alloys cannot be distinguishable in damping capacity from normal metals at that temperature. Accordingly, such alloys do not exhibit any damping capacity at a temperature higher than 100.degree. C. On the other hand, alloys of Zn-Al of the prior art have a high damping capacity at temperatures higher than 100.degree. C. However, as the temperature becomes lower, it decreases rapidly and becomes a very small value at room temperature. These alloys of Mn-Cu, Ni-Ti and Zn-Al are poor in cold workability and corrosion resistance.
Accordingly, it has been expected to provide a damping alloy having a high damping capacity, high cold workability and high corrosion resistance over wide range of temperature.